ASTM_F_1763_-_96.pdf

Designation:F 1763 96Standard Test Methods forMeasuring Contrast of a Linear Polarizer1This standard is issued under the fixed designation F 1763;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 These test methods describe measurement of polarizercontrast.A distinction is made between contrast,which is anintrinsic polarizer property,and extinction,which is a compari-son between two polarizers.1.2 These test methods are applicable to polarizers thatoperate in a transmissive mode at near-normal incidence.Angular or translative offset of the transmitted beam is accept-able if the entire transmitted beam power can be measured.1.3 The polarizer size or aperture is not limited by the testmethods,but the operator must appreciate that the contrast willbe an average over the beam spot on the polarizer.Contrastmeasured at one location on the aperture does not necessarilyapply to the entire aperture.1.4 These test methods are limited to wavelengths for whichthe tester can provide a collimated beam,and correctlymeasure changes in the transmitted beam power.The contrastobtained at one wavelength does not necessarily apply at anyother wavelength.1.5 The maximum contrast obtained by these test methods islimited by the dynamic range of the source-detector combina-tion.1.6 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.For hazard state-ment,see Section 7.2.Referenced Documents2.1ANSI Standard:Z136.1Safe Use of Lasers23.Terminology3.1 Definitions:3.1.1 contrast:C=t1/t2the ratio of maximum transmis-sion through a polarizer(t1)to minimum transmission(t2)when the polarizer is rotated in a light beam of infinite contrast.Contrast is an intrinsic property of a polarizer.3.1.1.1 Discussion Contrast can also be used to describethe degree of linear polarization of a light beam.In that case itis the ratio of linearly polarized light power in the maximumdirection(P1)to the minimum(P2).CL=P1/P2andPtot=P1+P2.An unpolarized or circularly polarized lightbeam has CL=1.A completely linearly polarized light beamhas C=.3.1.2 extinction,Xthe ratio of maximum to minimumtransmission of light through a pair of polarizers that arerotated with respect to each other.3X is an average between thetwo measured polarizers and is not necessarily applicable toeither polarizer taken alone.3.1.2.1 Discussion If the two polarizers have the samecontrast,then X=t1/2t2=(12)C.Extinction can be measuredwith unpolarized or polarized light.The inverse of X issometimes referred to as extinction ratio.The distinction isself-evident since X varies from 1 to and1xvaries from 1 tozero.3.1.3 leakage transmission,t2the ratio of minimum trans-mitted light power for a polarizer rotated in a light beam ofinfinite contrast,to the total light beam power without thepolarizer.t25 Pmin/Ptot(1)3.1.4 transmission,t1the ratio of maximum transmittedlight power for a polarizer rotated in a light beam of infinitecontrast,to the total light beam power without the polarizer.t15 Pmax/Ptot(2)4.Summary of Test Methods4.1 Three test methods are described in this standard.Thefirst method is a direct contrast measurement that requires alinearly polarized light source with high CL.The secondmethod is a comparison with a linearly polarized light sourcewith known CL.The third method is an indirect contrastmeasurement that can use an unpolarized or polarized lightsource of unknown CL.4.1.1 Direct Contrast MeasurementThis is the preferredmethod for measuring C of a single polarizer.This method canbe used if CL C for the polarizer to be tested.It is a simple,expedient,and accurate test method if a highly linear polarizedlight beam is available at the required wavelength.The sourcewill normally be a polarized laser beam in combination with a1These test methods are under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.06 on SiliconMaterials and Process Control.Current edition approved Dec.10,1996.Published February 1997.2Available from American National Standards Institute,11 W.42nd St.,13thFloor,New York,NY 10036.3Bennett,J.M.,and Bennett,H.E.,“Polarization,”Section 10 of the Handbookof Optics,W.G.Driscoll and W.Vaughan,Eds.,McGraw-Hill,1978.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.high-contrast prism polarizer.A tunable broad-band source canalso be used if a high-contrast polarizer is available for thewavelength of interest.In this test method the polarizer beingtested is rotated in the light beam and the maximum andminimum